Unseen UVs appear in Texture paint?
You have mesh artifacts and double vertices from modeling in your geometry. 



There are two possibilities to solve this. 


Tab into Edit Mode, hit W and select "Remove Doubles". You need to unwrap your model after that again.
In your UV/Image Editor window, hit A to select everything, turn on "Keep UV and edit mode mesh selection in sync" (see image below), switch to Face Select mode, then select all the faces you want to get rid of. Move your mouse to the 3D View and hit X and select "Faces" to remove them. 




Make sure to check and recalculate the face normals after that.